Brookhaven Spotlights: News from the March
2001 American Physical Society Meeting

NOTE TO EDITORS: "Brookhaven
Spotlights" is issued periodically to bring you up to date on some of the
latest newsworthy developments at the U.S. Department of Energy's Brookhaven
National Laboratory. The selected briefings below describe research that
Brookhaven scientists will present at the American Physical Society meeting to
be held March 12-16 at the Washington State Convention Center in Seattle,
Washington.

The following information is embargoed for
release at the time of each individual talk.

Research reveals secret of high-performance
transducers

Brookhaven's Beatriz Noheda will report on new advances in the
study of piezoelectric materials - materials that can be deformed by the
application of an electric field, or that produce an electric current when
physically deformed. One of the most important piezoelectric materials, known as
PZT (a ceramic), is used as a transducer for transforming the vibrations of
sound waves, for example, into electrical current and vice versa in devices such
as telephones, sonar systems, and ultrasound machines. Noheda will describe the
discovery of a previously unknown phase, or crystalline shape, for certain
compositions of PZT, which explains their very high piezoelectric response.

"With this new 'monoclinic' phase, you
no longer have to apply the electric field in the exact direction of the
deformation. This material has a lot more freedom to deform," Noheda says.
Scientists may now look for this "monoclinic" phase in other materials
and use them as well as PZT to make the next generation of solid-state
transducers, which could result in much more sensitive devices. This work was
done at the National Synchrotron Light Source.

Noheda's talk will take place in Room 602-603
on Tuesday, March 13, at 11:35 a.m.

Beatriz Noheda

Brookhaven's Tonica Valla will present his
group's latest efforts to understand the underlying mechanism for
superconductivity in copper-based (cuprate) materials that act as
high-temperature superconductors. Like traditional superconductors, these
materials carry electrical current with no resistance while in their
superconducting state. But Valla's studies at the National Synchrotron Light
Source reveal that they don't use the same mechanism.

In both traditional and
high-temperature superconductors, pairs of electrons carry the electric current,
but the "glue" that holds the pairs together may be different. Valla's
experiments give direct information about electronic states in these materials
and can uncover the interaction that causes pairing of electrons. "These
cuprate materials have properties that cannot be explained by conventional
theories," Valla says.

The motivation for understanding the mechanism is a practical one. The
new materials become superconducting at warmer temperatures than conventional
superconductors, which must be kept super cold by surrounding them with expensive
liquid helium. The cuprates Valla studies are superconducting at temperatures
"warm" enough to be chilled by less-expensive liquid nitrogen.
"If we understand how these high-temperature superconductors work, we might
be able to make them more efficient so that they can take the place of the more
expensive kind in magnets for accelerators, electronic circuits, or even more
exotic applications as superconducting railroads and motors," Valla says.

Valla will give this talk in Ballroom
6C on Tuesday, March 13, at 9:12 a.m.

Tonica Valla

New x-ray technique improves imaging of
breast calcifications

Brookhaven scientist Zhong Zhong and North Carolina
State University researchers Miklos Z. Kiss and Dale E. Sayers are investigating
a new technique called diffraction enhanced imaging (DEI) to detect and study
calcifications of breast tissue. Using DEI, the collaboration looked at a sample
of breast tissue with at least ten calcifications and made computer models of
the new imaging process to study its contrast mechanisms. This new method
significantly improves pictures of breast tissue compared to x-rays used in
mammography. Calcifications are associated with breast cancer, and their early
detection is crucial for diagnosis and treatment.

DEI was developed and tested at Brookhaven's
National Synchrotron Light Source (NSLS) by researchers from Brookhaven, the
Illinois Institute of Technology, North Carolina State University, and the
University of North Carolina. DEI reduces the x-ray scattering that makes for
blurry images and lack of contrast in mammograms. The new patented method may
one day replace mammograms.

Kiss will describe DEI in Room 606 on Friday, March 16, at 9:12 a.m.

Zhong Zhong

Scientists probe the properties of mixed
magnets

Brookhaven's Andrey Zheludev will review recent neutron scattering
studies of "mixed" quantum/classical magnets. Conventional magnets are
characterized by long-range magnetic order - where the magnetic fields of all
the individual atoms are oriented in the same or alternating directions. In
contrast, certain one-dimensional magnets become disordered when quantum effects
cause oscillations in the magnetic fields of individual atoms. "The
properties of such systems totally defy the classical picture of
magnetism," Zheludev says.

An outstanding problem in condensed matter
physics is understanding how classical and quantum magnets interact when
combined in a single material. Zheludev will describe the discovery and study of
the first known experimental example of such "mixed" magnets, found in
complex rare-earth nickel oxides. The most important finding is that dynamic
properties of these compounds have a unique dual nature, with features of both
quantum and classical magnetism.

This study deals with the most basic and fundamental aspects of material
magnetism. While unlikely to result in practical applications in the short term,
it contributes to the general understanding of how all magnets work.

Zheludev's talk will take place in Ballroom 6A on Wednesday, March 14, at
8:00 a.m.For more information on the APS meeting, go to: http://www.aps.org/meet/MAR01/.